Process of preparing 2.2&#39;-diamino-diphenyl-4.4&#39;-disulphonic acid



Patented Oct. 4, 1932 UNITED STATES PATENT OFFICE EDUARD TSCHUNKUR AND ERNST KRACHT; OF COLOGNE-MUIiI-IEIM, GERMANY, AS-

SIGNORS 'IO GENERAL ANILINE WORKS, INC., OF NEW YORK, N. 'Y., A. CORPORATION OF DELAWARE PROCESS OF PREPARING 2.2-DLAMINO-DIPHENYL-4A-DISULPHONIG ACID No Drawing. Application filed July 16', 1931, Serial No. 551,300, and in Germany July 21, 1930.

This invention relates to a process for the manufacture of 2.2-diamino-diphenyl-4.4- disulphonic acid. I

2.2-dinitro-diphenyl-4.4-disulphonic acid has been described in the publication of Ullmann and Prentzel (Berichte 38, page 726). The method of manufacture from 2-nitroaniline-t-sulphonic acid described therein is, however, too expensive for technical purposes.

In accordance with the present invention the said dinitro-diphenyl-disulphonic acid and further the corresponding diamino compound are produced from diphenyl in a simple manner and in a good yield and urity. The process of the invention is by sulp onating diphenyl to diphenyl-LA-disulphonic acid by means of an excess of concentrated sulphuric acid, monohydrate or oleum con taining about 20% S0 and then introducing two nitro groups into the diphenyl disulphonic acid by means of a sulphuric acidnitric acid mixture. The resulting dinitro disulphonic acid is then converted into 2.2- diamino-diphenyl-4s4c-disulphonic acid by means of known reducing agents, such as for example, iron and hydrochloric acid.

The following example illustrates the invention, without however, restricting it there- 100 kgs. of diphenyl are heated gradually to 90 C. with about 500 kgs. of sulphuric acid monohydrate and stirred for several hours at this temperature. The mixture is then cooled to 40 C. and 280 kgs. of mixed acid (33% nitric acid and 67% sulphuric acid) are caused to run in at about 40-50" C. and stirred for several hours at 80 C. Thereafter the liquor is poured on to ice and t h e 2.2-dinitro-diphenyl-LA-disulphonic acid is salted out with common salt, filtered by suction, washed with common salt solution and dried. V p

The sulphochloride of the resulting dinitro-diphenyl-disulphonic acid (after once crystallizing from lacial acetic acid) melts at MSG-167 C. 167 0.).

The 2.2-dinitro-diphenyl-4.4E'-disulphonic acid thus obtained is made into a paste with according to Ullmann 7 obtainable technically in such a simple and V smooth manner.

We claim 1. The process which comprises sulphonating diphenyl to form tAV-disulphomc acid, nitrating the diphenyl- LA-disulphonic acid, and reducing the 2.2-dinitro-diphenyl-4.4-

disulphonic acid to the 2.2-diamino-di phenyl-4.4'-disulphonic acid.

2. The process which comprises heating di-, phenyl in sulphuric acid monohydrate to 90 (3., keeping the reaction mixture at this temperature for several hours, allowing the reaction'mixture to cool down to 40 0., introducing nitrating acid, stirring for several hours at C. isolating the 2.2-dinitro-diphenyI-4AK-disulphonic acid and reducing the same with iron and hydrochloric acid.

In testimony whereof, We aflix our signatures.

EDUARD TSCHUNKUR. ERNST KRACHT. 

